Re:stopping medication--don't!.

[Guest guest]

Chuck gave me a very clear explanation of what might happen if you

suddenly go off medication. This was a few days or a week ago, and I

have looked back in the archives, can't seem to find it.

Gail

> > Thanks all for your helpful answers. Will take on board all the

> advice and will increase adrenals starting from tomorrow. I won't

be

> taking any armour for a day or two.Thanks again.

> >

> >

[Guest guest]

Gail,

You wrote:

> Chuck gave me a very clear explanation of what might happen if you

> suddenly go off medication. This was a few days or a week ago,

I sent this on June 14:

[begin old post]

Actually you don't want pre-pill status, for several reasons. First, if

you are symptomatic, all you may need is just a minor adjustment of your

dosage based on your current TSH reading. If you are going for the full

bank of other tests, the levothyroxin dosage can still be taken into

account in planning a change in either dosage or medications. You don't

need to go back to square one.

Finally, your body cannot return to your true pre-pill status for over a

month, a month of severe symptoms, some of which could cause permanent

damage.

> ... So, my question is-- how long would it take for all the T4

supplement to leave my body?

The average reported biological half life for T4 is about six days.

However, it varies with your health and activity level. You need about

6-10 half lives to reduce to a minimally measurable level. That amounts

to over a month.

If your thyroid is still producing, even partially, the chemical

feedback loop will first anticipate its response to the rapidly dropping

level, which can lead a carefully balanced system to a temporary

hyperthyroid condition and then to an even faster (and more symptomatic)

drop. This is called a paradoxical oscillation, and it is not something

to mess around with. Even a temporary hyperthyroid condition can trigger

cardiac problems.

I have read about this in the literature, but I am curious whether

anyone on the list has experienced temporary hyper- symptoms on missing

a dose or two. My sister told me she had, which is why I came to find

out about it.

[End June post]

Last October, I sent a bit more technical explanation:

[begin October post]

The concept of metabolic half-life is most useful for simple drugs that

are removed by something like a single liver enzyme. However, it is

defined as the time it takes for half of the dosage to leave the system,

not buildup. Instead, half life is connected to buildup in a reverse

sense. Generally, the shorter the half life (faster it is removed) the

longer it takes to build up to a steady state level.

Even such simple dose behaviors can be confounded by other factors. For

example, the half life of caffeine in healthy non-smoking adults is

about six hours. In a heavy smoker this is reduced to about three hours,

which may explain the appetites of those who imbibe both. Vitamin C and

aspirin similarly share a liver enzyme that removes them, which means

that taking either one reduces the effective half life of the other. If

you have a cold, you might want to take these two out of phase, every

two hours, instead of taking them at the same time. This will maximize

both their effects.

The elimination rate may vary with time, particularly if some part of

the metabolic pathway is exhausted or if it reaches an " accommodation "

level. This means that some drugs do not even approach steady state

levels until the production rate of an enzyme is saturated. Then the

drug level rapidly approaches the asymptote.

In this case, hormone replacement with synthroid is anything but simple.

The therapeutic effect comes from T3, which is a metabolic product of

the T4. Thus, we really have at least two half lives to consider. The

half life of T4 controls the rate at which T3 increases, while the

processes behind the half life of T3 remove T3 or transform it to other

metabolites. If you describe this mathematically considering only the

two half lives, you start with two coupled first order differential

equations. The solution has several terms, each with a combination of

exponentials in the half lives. The result is that the time it should

take to approach a steady state dose of T3 depends on the T4 input rate,

but it could well be a matter of about three weeks.

The problem is that this is not all that is going on. The T3 removal

rate depends on activity. The more you do, the faster you use it up.

Some T4 and T3 may also still be produced by what is left of the thyroid

gland itself. Other parts of the system affect T4 to T3 conversion,

storage, and re-release. Finally, and perhaps most influentially,

thyroid production is governed by a complex feedback system involving

TSH from the pituitary. The result is that buildup does not proceed in a

smooth manner. Instead, it tends to overshoot with sudden changes in

dose rate, resulting in oscillations above and below the ultimate steady

state level. It is these oscillations, and especially the high

excursions, which the usual gradual increase in synthroid dosage is

designed to avoid. A large over shoot on the hyperthyroid side can be

life threatening.

Thus, Carol's system might amount to a " moving target, " for which over

correction can be deadly or at least very uncomfortable. I was fortunate

that I was quickly fine tuned with synthroid in a matter of months and

have been rock steady ever since. However, if other variables play a

part, two years might not be enough to reach stability. Carol, I would

expect that an endo working with synthroid would have followed much the

same protocol as your GP with similar results. Switching docs might not

help, if you stay with synthroid alone.

OTOH, if T3 or TSH levels continue to move around on you, the only

solution might be to use a different medication, one that incorporates

some T3 directly, and which would allow day to day adjustments. I

certainly haven't needed that so far myself, but I can see where it

might be a useful alternative. Your current doc might even consider

this, if asked.

[End October post]

Hope this helps,

Chuck

[Guest guest]

Wow!! You are right on the ball! Must be nice to have just clear

brain function. For many years I have used the well-known

phrase " Sorry I can't think--I have fibrofog " . I'll take a copy this

time. I wonder what excuse I will use when my endocrine system gets

all sorted out...;-)

Gail

In hypothyroidism , Chuck B <cblatchl@p...> wrote:

>> I sent this on June 14:

>

> [begin old post]

> > [End June post]

>

> Last October, I sent a bit more technical explanation:

>

> [begin October post]

>